Computers won't recognise files on flash drives

Hi all, this is a weird problem I'm having. I tried plugging in two seperate USB drives into two different computers and neither computer will show the files that are on either USB drive.

Background is that I had some movies, books and things on one 8gb and one 32gb flash drive that I was transferring from my desktop to my laptop. The drives sat on top of my stereo for a month or two and when I just tried to plug in the drives to my laptop only a couple of the folders that were on the drive showed up. I tried transferring one of the folders to my laptop and it said 1.36gb was being transferred and it took a minute or so but when I clicked on the folder that had been moved to my laptop the movie file didn't show up. I thought maybe I had already transferred the folders and had deleted the contents but when I plugged the drives into my desktop to put some new files on them it says that the drives are still full up with the old files but neither computer will recognise the files. In My Computer it shows that the drives are full but when you click on them it says that they are empty.

Both drives have been used sparingly and are in very good condition, been kept indoors, etc, so I don't see why it would be a problem with the drives themselves, especially since the exact same thing happened to both drives. I just plugged in a third drive and my desktop recognises it, should I try and reformat the problem drives? As I say, both drives have never given me any problems before. Thanks a bunch for any help.

 

Note: I also tried scanning both drives and they both say they are working properly.

 

Don't set drives near anything that might have a magnet. (I learned this when we put a floppy near an old telephone).
stereos have speakers and speakers have magnets.